The present invention relates to apparatus for recording and reproducing information on magnetic tape, more particularly to an improved method of detecting the end of the magnetic tape.
Magnetic tape is widely used for recording and reproducing audio and video signals. The operating modes of the recording and reproducing apparatus commonly include a fast-forward mode and a rewind mode, in which the tape is transported at high speed. In these high-speed modes, it is desirable to reduce the tape speed shortly before the end of the tape is reached, to lessen the shock that occurs when tape travel halts abruptly at the end of the tape. For this purpose, it is necessary to detect the approaching end of the tape.
A known detection method is to detect the rotational speeds or periods of the two reels on which the tape is wound, and monitor the ratio between the two speeds or periods. A disadvantage of this method is that it requires the simultaneous monitoring of the rotation of two reels, and repeated ratio calculations.
Some types of tape have a control track on which a control signal with a pulse waveform is recorded. The approaching end of the tape can then be detected by monitoring the number of control pulses per revolution of the supply reel. A disadvantage of this method is that it fails completely if the control signal is missing. Furthermore, even when the control signal is present, individual control pulses may be missing, or may not be picked up, causing the end of the tape to be detected at the wrong place.